If that's the case I prefer Josephine (Jo) Grant. We got to see a young "fresh out of school" girl grow up to become an independent and caring woman and her travels with the Doctor helped mold her into that grown-up woman.

Also it helped the Doctor adjust to his time on Earth as he took a kind of "father-figure" approach to Jo and became her mentor.

Not-so-much Liz - she was already a scientist and full character when she was brought into UNIT and she had no real direction to grow.

People often say Jo is the companion 'screamer' archtype of the series, but back then - there was no such archtype. She was fun and independent, cute as a button and a tough cookie when it came time to duel with the Master or knock King Peladon off his indifferent backside. She wasn't all in your face about feminism like some favorite companions were (Cough!SaraJaneCough!) but still stood up for the ladies when the occaision made it possible. Plus anyone who quotes the Beatles is tops in my book.

Liz too was a good character, inheriting some of the old lines that Zoe would have spoken in the 2nd Drs run - but as Pertwee got a foothold on the series, and he made the role his own he made it clear that he wanted his companion to be an assistant that he could rescue and explain things to - rather than a companion to 2nd guess him.